The present invention relates to waveguide antenna, and particularly to ridged waveguide slot array antennae.
Waveguide slot array antennae are well known in the art, and are typically employed for providing high power capability in applications, such as base station transmitting antenna arrays.
FIG. 1A illustrates a conventional vertically-polarized waveguide slot array 100 as known in the art. The array 100 includes a waveguide slot body 110 which is operable to support the propagation of a signal along a longitudinal axis 112 (z-axis) of the waveguide slot body 110. Transverse to the longitudinal axis 112, the waveguide slot body 110 defines a waveguide aperture having a major dimension 113 (along the x-axis) and a minor dimension 114 (along the y-axis). The major dimension 113 defines the lowest frequency of operation for the array 100, and is typically 0.5λ in its dimension. The waveguide slot body 110 further includes edge slots 122 and 124, each angled a in respective positive and negative angular orientations relative to the axis of the minor dimension 114. An end cap 130 is located at the top of the array 100.
FIG. 1B illustrates typical radiation patterns 150 for the vertically-polarized waveguide slot array 100 of FIG. 1A. The patterns 150 include an azimuth radiation pattern 152 and an elevation pattern 154. The azimuth radiation pattern 152 exhibits 8 dB variation, as shown.
FIG. 2A illustrates a conventional horizontally-polarized waveguide slot array 200 with horizontal polarization as known in the art. The array 200 includes a waveguide slot body 210 which is operable to support the propagation of a signal along a longitudinal axis 212 (z-axis) of the waveguide slot body 210. Transverse to the longitudinal axis 212, the waveguide slot body 210 defines a waveguide aperture having a major dimension 213 (along the x-axis) and a minor dimension 214 (along the y-axis). The major dimension 213 defines the lowest frequency of operation for the array 200, and is typically 0.5λ in its dimension. The waveguide slot body 210 further includes longitudinal slots 220, each slot offset a predefined distance from a center line defining the major axis 212 of the waveguide body 210, adjacent slots offset in opposing directions from the center line. An end cap 230 is located at the top of the array 200.
FIG. 2B illustrates typical radiation patterns 250 for the horizontally-polarized waveguide slot array 200 of FIG. 2A. The patterns 250 include an azimuth radiation pattern 252 and an elevation pattern 254. The azimuth radiation pattern 252 exhibits 4 dB variation, as shown.
As can be observed, the azimuth radiation patterns for each of the conventional vertically and horizontally-polarized waveguide slot arrays vary significantly over the coverage area, meaning that signal levels over these coverage areas vary greatly as a function of the user's position. As a result, a high power transmitter or a high gain antenna is needed to ensure that the minimum signal level is provided to all users, independent of their location. Accordingly, although slot arrays are suitable for high power transmission and reception applications, they cannot be fully deployed in applications where more uniform coverage is needed.
What is accordingly needed is a waveguide slot array which can provide a more uniform radiation pattern.